Multiple pass liquid cooling jacket



Nov. 7, 1961 B'. BE RNSTEIN ETAL MULTIPLE PASS LIQUID COOLING JACKET Filed Feb. 7, 1958 INVENTORS, BERNARD BERNS TE/IV CARSON M. WHEEL ER ATTORNEY 3,098,063 Patented Nov. 7, 1961 free 3,008,063 MULTIPLE PASS LIQUID COGLING JACKET Bernard Bernstein, Belleviiie, and Carson M. Wheeler, Montclair, NJ., assignors to Nuclear Corporation of America, line, Denville, NJ, a corporation of Delaware Filed Feb. 7, 1958, Ser. No. 713,830 8 Claims. (Cl. 31324) The present invention relates to discharge devices or tubes capable of delivering large amounts of power and more particularly to a highly eificient fluid-cooling means associated with the anode of a high-power amplifier or rectifier tube.

In the design of high-power electron tubes utilizing fluid-cooled anodes, certain of the physical parameters of the anode and of heat-dissipation elements associated therewith are determined by considerations other than those of convenience of physical design alone. Thus, in high-power amplifier or rectifier tubes utilizing hollow cylindrical anodes, this being the type of tube with which the present invention is particularly concerned, the internal diameter of the anode is determined by the physical size of other electrodes of the tube and also by the overall electrical characteristics of the tube. The anode is surrounded by a jacket having an external diameter determined by the quantity of heat to be dissipated therefrom per unit of time, which latter factor is determined by the amount of power to be delivered by the tube. The jacket is coaxial with the anode and the fluid-cooling medium is directed between the anode and the jacket to effect rapid heat transfer from the former member to the latter member.

The rate at which heat may be transferred from the anode to the jacket of a fluid-cooled electron tube is determined by the surface velocity of the fluid relative to the anode, the heat-conductivity and viscosity of the fluid and the area of contact between the external surface of the anode and the fluid. Ideally, the fluidcooling medium should be dispensed with by providing a hollow-cylindrical, heat-conductive member having an internal diameter determined by the electrical properties of the anode and having an external diameter determined by the square inches of heat dissipating surface required for the tube. The difliculty with such an arrangement is that where large amounts of power are to be delivered by the tube and therefore large quantities of heat must be dissipated, the hollow-cylindrical anode would have extremely thick walls. Since these anodes are normally made of copper, because of the heat transfer properties of this material, the anode would be highly expensive and extremely heavy. The latter consideration is important not only with respect to cost and to ease of handling the tube, but also from the point of view of tube structure, since a heavy and bulky anode would greatly complicate and increase the cost of the structure.

In consequence, rather than utilize a solid anode having an external diameter equal to the external diameter as determined by the square inches of heat-transfer surface required, it is common to pass a heat-conductive fluid between a relatively thin-walled anode and a cooling jacket, the fluid being employed to transfer the heat from the anode to the cooling jacket. As previously indicated the heat transfer characteristics of such a system depend upon the surface velocity of the fluid, the heatconductivity and viscosity of the fluid and the heattransfer surface of the anode. The heat-transfer surface of the anode may be increased by utilizing heat-conductive fins extending radially outward from the anode into contact with the sleeve. Such an arrangement not only increases the surface area of the anode in contact with the heat-conductive liquid but also provides for direct heat-transfer from the fins to the hollow sleeve which is in contact with the outer edges of the fins. This arrangement is wellknown in the art but here again the number and thickness of fins which may be employed is restricted by the cost and physical weight of the material utilized.

To overcome some of the difliculties experienced in effecting heat-transfer between an anode and a fluidretaining sleeve, Rheaume in his Patent No. 2,693,347 discloses apparatus wherein the spacing between the anode and the sleeve is minimized in order to impart a high velocity to the fluid so as to increase the turbulence of the fluid and thereby increase the transfer of heat from the anode to the sleeve. The difliculty with the Rheaume device is that the spacing between the anode and sleeve can be minimized only by increasing the diameter of the anode which results in an anode of excessive weight and cost if the Rheaume system were applied to high power tubes.

The desirability of increasing the velocity of the cooling fluid as taught by Rheaume is unquestionable and it has been suggested to increase the size of the pump utilized for circulating the fluid. Here again considerations of cost, size and portability limit the extent to which this course may be employed.

In addition to the limitations inherent in the prior art attempts to increase the power handling capabilities of fluid-cooled anodes, as indicated above, each of these methods requires discarding or drastically modifying existing equipments whenever the power handling capabilities of an installation mus-t be increased. A related problem may arise where, due to electrical circuit considerations it may be necessary in a system of a given design to maintain the heat dissipation capabilities of the system constant, while utilizing a fluid having a lower heat conductivity than originally contemplated. The circulation of the fluid between the anode and shield requires fluid to be conveyed through a pump external to the tube. In high-power amplifier and rectifier tubes, the anode is operated at relatively high voltages and where a highly conductive fluid is utilized for cooling, certain difliculties arise due to the fact that this fluid maintains all of the metal parts in contact with the fluid at a high voltage. In addition, in amplifier tubes, the flow of the conductive fluid externally of the tube is bound to effect some degradation of signal due to excessive capacity to ground. It is well-known that the heat and electrical conductivity of a fluid are directly related and therefore if it is essential that the electrical conductivity of the fluid be reduced, means must be found for at least maintaining the heat-dissipation potential of the system constant. As indicated above this may be accomplished by increasing the velocity and therefore turbulence of the fluid by decreasing the spacing between the anode and sleeve or by increasing the size of the pump but such procedures are expensive and in many cases impractical if not impossible.

It is therefore an object of the present invention to increase the heat-dissipation capabilities of a power amplitier or rectifier having a thin-walled, hollow-cylindrical anode and an external shield coaxial therewith by increasing the velocity of the fluid flowing over the anode with out necessitating changes in the fluid circulation apparatus.

It is another object of the present invention to provide an electron tube having a hollow-cylindrical anode and a fluid circulating system for cooling the anode wherein the heat-dissipating capabilities of a given apparatus is greatly increased by increasing the velocity of flow of the fluid without requiring any change in the capacity of the fluid circuating members.

It is another object of the present invention to provide a fluid circulating system for flowing a fluid over the surface of a radially-finned, hollow-cylindrical anode wherein a high velocity fluid stream is obtained by requiring the fluid to flow over the finned portions of the anode in multiple passes rather than in a single pass as is conventional.

In the apparatus of the present invention there is provided a power amplifier or rectifier tube having a hollowcylindrical anode and a plurality of radial fins extending outwardly therefrom and into contact with an external sleeve coaxial with the anode. A heat-conductive fluid, preferably a liquid, is pumped through the space between the anode and the sleeve so that the fluid is caused to flow over the fins and transfer heat from the fins to the conductive fluid. Normally, and in the prior art devices, this liquid is caused to flow over all of the fins in one pass so that the input and output velocity of the liquid to the anode structure is substantially equal to or slightly less than the surface velocity of the liquid over the radial fins of the anode.

In accordance with the present invention, the fluid is allowed to flow over only a predetermined number of the radial fins in one pass over the fins, and is constrained to flow serially over equal numbers of fins until all of the fins have been contacted by the fluid. Thus, the fins may be divided into two or more equal groups and the fluid constrained to flow over each of the groups in succession. In this manner, although the input and output velocity of the fluid remains substantially unchanged and the capacity of the flow-inducing member or pump is maintained the same, the surface velocity of the fluid with respect to the fins is increased by a factor proportional to the number of serial flow paths provided since the cross-section of the flow path has been reduced by this same number.

The multiple pass flow pattern of the present invention may easily be established by providing hollow end members which in conjunction with the external sleeve define a sealed space about the anode, and providing bafi les which extend between these hollow end members and the fins to define a number of flow paths through the sealed space.

In consequence, with a small number of inexpensive, light-weight and relatively small baflle structures, the heat-dissipation capability of a conventional fluid-cooled power amplifier or rectifier tube may be greatly increased without disturbing any of the other elements of the tube or apparatus employed in the fluid flow system. As a result of this extremely simple and inexpensive apparatus and method for increasing the surface velocity of the cooling fluid with respect to the external surface of the anode of the tube, the power-handling capabilties of the tube may be greatly increased or the power-handling capabilities may be maintained the same while the 'heatconductivity and therefore the electrical-conductivity of the heat transfer fluid may be reduced so as to improve the electrical characteristics of the tube.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a side view partially in cross-section of a high-power rectifier tube incorporating the apparatus of the present invention;

FIGURE 2 is a perspective view of a discharge device employing the apparatus of the present invention; and

FIGURE 3 is a cross-sectional view taken along line 3-3 of FIGURE 1.

Referring specifically to FIGURES 1 and 2 of the present invention, there is provided a high-power electron discharge device generally designated by the reference numeral 1. The discharge device includes an evacuated glass envelope 2 having sealed in the left end thereof,

as viewed in FIGURE 1, filament input terminals 3 and 4 which are connected to two filament leads 6, only one of which is illustrated. The leads 6 are supported on and extend along opposite sides of a rod 7 that is Sealed in and extends from the left end of the glass envelope 2, through the center of the envelope and along the axis of a region defined by the center bore of a hollow-cylindrical anode 8. The anode 8 is secured to the right end of the glass envelope 2 by suitable means to be described. Secured to the rod '7 in the region of the anode 8 is a filament 9 having its two ends connected to the filament leads 6.

Theanode 8 which is made of highly heat-conductive material, such as copper, is secured to one end of a hollow metal sleeve 11 which has its opposite end secured to and sealed in the right end of the glass envelope 2. The seals between the hollow sleeve 11 and the envelope 2 and the anode 8 and the sleeve 11 are gas-tight seals which in conjunction with an anode plug 12 provides the gas-tight tube 1. The tube 1 is evacuated or filled with a suitable gas at a proper pressure to provide a high-power rectifier tube.

During operation of the tube 1, a considerable amoun of heat is generated which must be rapidly dissipated so as to prevent undue heating not only of the anode 8 but also of the filament 9.

In order to provide for adequate cooling of the anode 8 there is provided a plurality of heat-radiating fins 13 extending radially outward from the external surface of the anode 8 into contact with a hollow-cylindrical body 14 that is disposed about the radiating fins 13. The body 14 is coaxial with the anode 8 and extends for a short distance past the right end of the anode 8 and fin assembly, andterminates in an end wall 15 with diametricallyopposed circular apertures 16 and 17 extending therethrough. An inlet pipe 18 extends to a source of cooling fluid (not. illustrated) and communicates through the aperture 17 with a cylindrical region 20 subsisting between the bottom wall 15 of the body 14 and the left end of the anode 8. An exhaust pipe 19 communicates with the region 20 through the aperture 16 and is employed to return the cooling fluid to the aforesaid fluid pump.

The region 20 between the left end of the anode 8 and the bottom wall 15 of the body 14 is divided into three compartments, and reference is made now specifically to FIGURE 3 of the accompanying drawings, by two baflles 21 and 22. The bafiles 21 and 22 are generally U-shaped members having divergent legs lying along the radii of the cylindrical body 14 and including between their respective pair of legs a quarter segment of the cylindrical region 20. The baflle 21 defines a quarter segment surrounding an outlet aperture 16 while the baflle 22 defines a quarter segment surrounding the inlet aperture 17 in theend wall 15. The base of each of these baffles extends across the bottom of the anode 8 and each of the legs extends radially outward from the base in alignment with one of the fins 13 so that the legs of the members 21 and 22 effectively extend four of the fins 13 into engagement with the end wall 15 of the body 14 and therefore the segments defined by the baflles 21 and 22 are effectively sealed from the remainder of the region 20. In con-sequence of the above arrangement, fluid entering through the inlet aperture 17 in the end wall 15 is initially constrained to flow longitudinally of the anode 8 and over the baffles 13 confined within the region defined by the legs of the bafile 22.

The left end of the hollow cylindrical body 14, as viewed in FIGURES 1' and 2, mates with an end cap 23 having substantially the shape of a donut, split in half along its horizontal center plane. The cap 23 is in sealed engagement along its outer edge with the end of the body 14 and is in sealed engagement with the anode 8 along its inner edge, to provide an end seal for the liquid space at the right end of the anode 8 and the fins 13. Two semi-circular discs 24, only one of which is illustrated in FIGURE 2 and both of which are diagrammatically illustrated in FIGURE 3, are disposed at diametrically opposed positions within the end cap 23. The baffles 24 are bonded to the end cap 23 and extend radially thereof in alignment with predetermined bafiies 13 so as to divide an upper chamber 25 defined by the cap 23 into two semi-circular segments. The baflles 24 are disposed half-way between the legs of the bafiies 21 and 22, located at the other end of the anode structure. Specifically, and reference is made to FIGURE 3 wherein the baflies 24 are represented by dashed lines to illustrate their location with respect to the members lying in the plane of this figure, each batfie 24 is located half-Way between One of the legs of the baffle 21 and one of the legs of the bafile 22 so that a four-pass liquid system is provided by the apparatus of the invention.

In operation, the liquid that enters through the inlet pipe 17 flows over the radiating fins 13 included within the segment defined by the legs of the bafiie 22, and enters the end cap 23. Upon entering the end cap 23, and reference is now made to FIGURE 3 of the accompanying drawings, the fluid divides into two portions. Approximately half of the cooling fluid flows clockwise over the tops of the fins lying in a segment as determined by one of the baflies 24 and another half of the fluid flows counter-clockwise over the tops of the radiating fins l3 lying in a /8 segment of the cylindrical structure as defined by the other baflle 24. Both halves of the initial body of fluid then flow over the surfaces of the radiating fins 13 in the aforesaid /s segments and into the portion of the chamber 20 lying between the legs of the baflies 21 and 22 and the cylindrical walls of the body 14. It will be noted that the two bodies of fluid mingle again in this chamber and then proceed over the radiating fins l3 lying'in two distinct A; segments as defined by the baffles 24 and the legs of the baflle 21. The two fluid streams flow together in a quarter segment of the end cap 23 as defined by the baflle 21 and return over the fins 13 to the chamber 20 and out through the aperture 16 to a flow inducing pump or mechanism.

It may be seen from the above that the fluid has been constrained by the bafiies 21, 22 and 24 to flow over the radiating fins 13 in multiple serial passes and in the specific arrangement disclosed, the fluid flowed over one continuous quarter of the batfles, then in two serial passes over two separate groups of battles each totalling a quarter of the 'baffles and then over a single group of one quarter of the baflles 13 to the outlet pipe 16. In consequence of this arrangement, although the input and output velocity of the fluid is substantially the same as if the fluid flowed over the radiating fins in a single pass, the actual velocity of the fluid adjacent the radiating fins 13 has been increased by a factor of four over the previously mentioned prior art configurations, and as a result the turbulence of this fluid is greatly increased.

It is an established fact that heat transfer through a fluid medium increases in proportion to the turbulence of the stream and specifically the rate of cooling is proportional to 0.8 power of the stream velocity. Since the velocity of the fluid in the present system has been increased by a factor of four in the specific embodiment illustrated, it is apparent that either the rating of the tube 1 may be increased or if it is desired to decrease the electrical and therefore heat conductivity of the fluid cooling medium, this may be accomplished Without a reduction in the heat-dissipating capability of the system.

It will be noted that the only additional parts required for etiecting an increase in the power handling capabilities of the system is eflected by the addition of only four parts over the conventional fluid system and yet the turbulence of the fluid has been increased to such an extent that the capacity of the tube has been increased at least 30% over its capacity in a system where the fluid flowed over the radiating fins 13 in a single pass. It is obvious that the number of passes which the fluid is constrained to make over the radiating fins may be varied in a particular system and with regard to the four pass system the particular arrangement illustrated for effecting four passes is not limiting since other baffle arrangements may be employed for the same purpose. There are limitations on the number of passes which may be made since if the number is excessively increased, the resistance to fluid flow in the system increases to such an extent that the input and output fluid velocities are reduced to a point where the entire capacity of the system is reduced. However, within reasonable limits the number of passes which the fluid may be constrained to make over the radiating fins may be varied so as to meet a wide range of system requirements for increased heat dissipation characteristics or decreased conductivity of the fluid utilized for cooling.

While we have described and illustrated one specific embodiment of our invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What We claim is:

l. A fluid cooled electron discharge device comprising a hollow cylindrical anode, a plurality of axially-extending heat-conductive fins spaced about said anode and extending radially outward therefrom, a hollow cylindrical sleeve coaxial with and disposed about said anode and in contact with said fins, means for connecting the space between said anode and said sleeve to a source of cooling fluid and baflie means coacting with said fins to define predetermined arcuate segments in the space between said anode and said sleeve and for causing the fluid to flow serially through predetermined arcuate segments.

2. A fluid cooled electron discharge device comprising a hollow cylindrical anode, a plurality of axially-extending heat-conductive fins spaced about said anode and extending radially outward therefrom, a hollow cylindrical sleeve coaxial with and disposed about said anode and in contact with said fins, a fluid delivery orifice and a fluid discharge orifice and baffle means for causing the fluid flowing from said delivery orifice and to said discharge orifice to pass serially through equal arcuate segments of the space between said anode and said sleeve, each of said segments including a plurality of passages between said conductive fins.

3. A fluid cooled electron discharge device comprising a hollow cylindrical anode, a hollow cylindrical sleeve coaxial with and disposed outwardly of said anode, a plurality of heat-conductive fins extending axially of said anode and radially outward therefrom into contact with said sleeve, end members disposed at each end of said anode and defining compartments communicating with the space between said anode and said shield, means for effecting flow of cooling fluid from compartment to compartment over said fins, and battles disposed in said compartments to cause said fluid to pass through. equal arcuate segments of the space between said anode and said sleeve, serially.

4. A fluid cooled electron discharge device comprising a hollow cylindrical anode, a sleeve disposed coaxial with said anode, a plurality of heat-conductive fins extending radially outward from said anode into contact with said sleeve, end closure members cooperating with said sleeve to define end compartments in communication with the space between said anode and said sleeve, fluid inlet and fluid outlet means connected to at least one of said compartments and b affle means disposed in said compartments for defining a fluid flow path between said fluid inlet and outlet means, which flow path extends serially through equal arcuate portions of said space between said anode and said sleeve.

5. The combination according to claim 4, wherein said means for defining the fluid flow, comprises a plurality of baffles extending between certain of said fins and said end closure members.

6. A fluid cooled electron discharge device, comprising a hollow cylindrical anode, a hollow cylindrical sleeve generally coaxial with and disposed outwardly of said anode, a plurality of heat conductive fins extending axially of said anode and radially outward therefrom into contact with said sleeve to define a plurality of axially directed passages, an upper end closure extending from said anode to said sleeve to define an annular compartment above said fins, a lower end closure connected to said sleeve below said fins to define a lower compartment below said fins, means including lower baffles connected to certain of said fins for dividing said lower compartment into at least three portions, a fluid inlet and a fluid outlet connected respectively to first and second of said portions of said lower compartment, and at least two upper baffles located in said upper compartment and connected to individual ones of said fins to divide said upper compartment into at least two portions, each of said upper baflles being connected to a fin having at least one passage on each side communicating with a portion of said lower compartment other than said first and second portions of said lower compartment.

7.- A fluid cooled electron discharge device, comprising a hollow cylindrical anode, a hollow cylindrical sleeve generally coaxial with and disposed outwardly of said anode, a plurality of heat conductive fins extending axially of said anode and radially outward therefrom into contact wth said'sleeve, an upper end closure extending from said anode to said sleeve to define an annular compartment above said fins, a lower end closure connected to said sleeve below said fins to define a lower cylindrical compartment below said fins, means including lower baffies alined with and connected to certain of said fins for dividing said lower compartment into at least three portions, a fluid inlet and a fluid outlet connected respective ly to first and second of said portions of said lower compartment, and at least two upper baflles located in said upper compartment alined with anconnected to individual fins to divide said upper compartment into at least two portions, each of said additional baflies being alined with a fin having at least one pass-age on each side communicating with a portion of said lower compartment other than said first and second portions of said lower compartment.

8. A fluid cooled electron discharge device, comprising a hollow cylindrical anode, a hollow cylindrical sleeve generally coaxial with and disposed outwardly of said anode, a plurality of heat conductive fins extending axially of said anode and radially outward therefrom into contact with said sleeve, an upper end closure extending from said anode to said sleeve to define an annular compartment above said fins, a lower closure connected to said sleeve below said fins to define a lower compartment below said fins, means including lower baflles connected to certain of said fins for dividing said lower compartment into a plurality of portions, at least two upper baffles located in said upper compartment and connected to individual fins other than the fins to which said lower bafiles are connected to divide said upper compartment into a plurality of portions, and a fluid inlet and a fluid outlet connected respectively to different of said portions of said upper or lower compartments.

References tilted in the file of this patent UNITED STATES PATENTS 1,285,806 Schaefer Nov. 26, 1918 1,978,424 Gebhard Oct. 30, 1934 2,235,669 Conlclin et a1 Mar. 18, 1941 2,312,465 Zodtner Mar. 2, 1943 2,317,442 Chevigny Apr. 27, 1943 2,440,245 Cheviguy Apr. 27, 1948 2,441,971 Litton May 25, 1948 2,512,373 Pakala et a1. June 20, 1950 2,693,347 Rheaume Nov. 2, 1954 2,829,290 Von Warmerdom Apr. 1, 1958 FOREIGN PATENTS 866,017 France June 13, 1941 

